I've only been able to treat him with aquarium salt and 100% water changes every day. He is currently in a "hospital" tank so it would be easier to treat/clean. It's been 3 days of treatment now.

My question is...I should have my triple sulfa tomorrow so do I use that or should I try to heal him with the aquarium salt? He does not act like a sick fish at all. He is very lively and alert. He's eating, granted it's flakes, but it's something. The only sign of illness is the one small red streak on his bottom fin and the fact that he's missing a part of that fin. It doesn't seem to be affecting him. He has no new tears and it even looks like he's getting new colors in.

Housing
What size is your tank? 2 gallon hospital tank until he gets better
What temperature is your tank? 78 degrees, it doesn't seem to get any warmer.
Does your tank have a filter? not in the current hospital tank
Does your tank have an air stone or other type of aeration? no
Is your tank heated? yes
What tank mates does your betta fish live with? none

Food
What type of food do you feed your betta fish? right now he's eating flakes
How often do you feed your betta fish? since he didn't eat for who knows how long I've been feeding him just a little bit at a time up to 3 times a day.

Maintenance
How often do you perform a water change? since I've been treating him with the aquarium salt, every night
What percentage of the water do you change when you perform a water change? for now 100%
What type of additives do you add to the water when you perform a water change? water conditioner and aquarium salt

Water Parameters:
Have you tested your water? If so, what are the following parameters? I have not tested the water

Ammonia:
Nitrite:
Nitrate:
pH:
Hardness:
Alkalinity:

Symptoms and Treatment
How has your betta fish's appearance changed? He seems better. Unclamped fins, more colors, less ragged edges.
How has your betta fish's behavior changed? he's very alert and active now
When did you start noticing the symptoms? I bought him Sunday night and by Monday night part of his bottom fin fell off!
Have you started treating your fish? If so, how? Aquarium salt in a hospital tank with 100% water changes every night. I also don't have the aquarium light on him so he doesn't get stressed. He has the light from the room though
Does your fish have any history of being ill? He's been ill since I've had him, 3 days now
How old is your fish (approximately)? I've only had him 3 days

So what would you do? I would hate to over medicate him, but I don't want him to get worse. He's been doing so well. I'm very attached to the little guy and I've got faith in him! I just need advice from the experienced people out there on my next steps.

Here's a dark pic or two from today...like I said I don't have the aquarium light on. The pics aren't the best.

That's what I was thinking too. I'm so torn because I want to do the best for him. The red mark hasn't gone away at all, but he's doing good otherwise. I just would hate to give him meds when he's improving on the salt, but I also know nothing about septicemia and don't want him to take a turn for the worse if it spreads. I guess it will just be a judgemental call. Regardless I'll have the sulfa here so maybe I could try the salt a bit longer and if no improvement try the med?

I have found that when treating a Betta-it is important to support the immune response and give them the tools to take care of the problem themselves.

Its hard for me to tell much by the pic-but what I would recommend-Fresh, dechlorinated tannin stained water treatment and since you already started the salt continue that to complete the 10 day treatment.

Premix your treatment water in a 1gal jug of dechlorinated water-Add the salt 2tsp/gal and a tannin source-Using the premixed treatment water-make 50% water changes daily to every other day-I wouldn't make any 100% during treatment since that can be a stress point.

Thank you for the reply! What would the tannin source be? How much? Where would I get it?

I was wondering about the water changes because with yesterday's water change he did seem stressed, but he's still doing very well. I just don't want to traumatize the poor guy with unnecessary changes.

What I use...naturally dried and fallen from the tree Oak leaf...about 20 crushed/gallon of premixed treatment water. Or IAL (Indian almond leaf) usually you have to get these online-use 1 large crushed/gallon of premixed treatment water.

You can't overdose with tannins and you can use them long term. The tannins contain antibacterial/fungal properties, help to ease stress, toughen scales/fins and can lower pH slightly with long term use.

I no longer recommend 100% water changes with treatments in most cases-Based on further experiments I conducted. However, there are some exceptions.
I recommend-25-50% water changes using premixed treatment water-from daily to twice weekly-depending on the problem at hand and overall tolerance of the Betta itself to water changes.

Betta don't create as much byproduct as some may think-Most water quality problems stem from poor quality foods, overfeeding and leaving excessive amounts of uneaten food for too long.

Bettas as with most fish-its the immune response that is most important in regards to getting sick and treatments in general. Stress is the biggest factor that can compromise the immune response and why it is so important to limit stress factors as much as you can-With that said, sometimes we still have to do things that can be stressful for the Betta and this is when we need to weigh options....The lesser of two evils...so-to-speak....Often it will be a judgment call on your part.

By premixing your treatment water in a 1gal jug of dechlorinated water-adding the salt and tannins. This will give you more control with providing the therapeutic dosages when making partial water changes. It also allow the salt to fully dissolve and tannins to steep longer.
The longer the tannin steep-the more tannins released-the darker the water-the better the Betta will like it.

In a pinch-you can use decaf green or black tea as the tannin source, however, due to how it is processed-it may not contain the antibacterial/fungal properties-since that bacteria is killed in temps greater than 110F. But, the tanned water itself can be helpful for stress.
Use one decaf tea bag per gallon of premixed treatment water-

So if we didn't do a water change tonight Phoenix would be ok? No water change and no salt would still equal a day of treatment, right? Because he got fresh water and salt last night? Today would be day 4 of treatment with the aquarium salt.